1. Field of the Invention:
The present invention relates to communication systems. More specifically, the present invention relates to coherent data communication systems employing multiple data rates.
While the invention is described herein with reference to illustrative embodiments for a particular application, it is understood that the invention is not limited thereto. Those of ordinary skill in the art will recognize additional embodiments and applications within the scope thereof.
2. Description of the Related Art:
In many digital communication systems, data is transmitted at one data rate for acquisition and a second data rate for communication. Typically, the first data rate is low to facilitate acquisition while the communication data rate is high. In other applications, three or more data rates may be employed.
Conventional multiple data rate communication systems utilize separate demodulators for each data rate transmitted. In some applications, it is desirable to minimize the number of modulators used for data communication. In noncoherent systems, i.e., those that do not utilize phase data to assist in the demodulation of a received signal, a separate tone or subcarrier frequency may be used to designate the data rate. Unfortunately, this approach is unsuitable for the power efficient coherent communication schemes.
For the power efficient coherent communication system, a single demodulator could be used if the data rate could be detected. Once so detected, the parameters, filters, switches, and etc. of the demodulator could be automatically adjusted to optimize the performance of the demodulator for the data rate being transmitted. Thus, the related art demonstrates a need for a multiple data rate detector for coherent communication systems.